1. Field of the Invention
The present invention relates to a system diagnostics and control system for an apparatus having an induction motor and a heater and more particularly to a control for a clothes dryer having a split phase induction motor wherein operations of the dryer are controlled in response to phase angles of the motor and in response to one or more temperature sensors.
2. Description of the Prior Art
A control system for motors and for various appliances with motors is shown in U.S. Pat. No. 4,481,786, issued Nov. 13, 1984, and entitled ELECTRONIC CONTROL FOR A DOMESTIC APPLIANCE (Bashark I). The control system employes a ferrite core sensor having a primary winding that is formed of two turns of the run winding of the motor, typically an AC induction drive motor. The sensor has a single turn secondary winding that forms a sense winding coupled to a motor phase monitoring circuit. The sense winding provides a signal representing a polarity change in the run winding current. The current polarity change signal is used by the motor phase monitoring circuit to provide a voltage compensated motor phase angle pulse to a microcomputer for the appliance to control various operations of the appliance.
In particular, Bashark I teaches a control for a dryer wherein a digital representation of the motor phase angle pulse is used by the microcomputer to monitor the operation of the motor under the loading created by the clothes being tumbled in the dryer drum. The motor phase angle representation is used by the microcomputer to calculate a clothes tumble number by summing the absolute difference between given sums of the phase angle representations which are then used to generate a control signal at a given tumble number threshold for terminating the operation of the motor.
Bashark I also teaches that the same or a similar control circuit may be used to monitor the motor of other appliances, such as an air conditioner, a dishwasher, an automatic washer, and a refrigerator and to provide other types of information about the operation of these appliances. However, the disclosure in Bashark I was limited to monitoring only motor characteristics and was further limited in the types of information obtained from analyzing the phase angle information and the types of functions controlled as a result of obtaining the phase angle information. Specifically, Bashark I teaches a means of determining clothes dryness by detecting when the long-term average motor torque is no longer decreasing. However, average motor torque includes a significant torque burden due to drum gasket friction. The present invention introduces a much more sensitive means of processing the motor phase information which does not involve computation of the long-term average motor torque. Furthermore, Bashark I used only the single motor sensor and did not suggest how additional information could be obtained from other sensors advantageously interacting with the motor phase angle sensor. The present invention is directed to providing these advantageous features to the control as well as providing various additional improvements to motor sensors and controls generally.
It is known to use various single purpose sensors to monitor the condition of a dryer or the clothes load within the drum of the dryer. For example, it is known to detect a blocked lint filter using fluid pressure measurements, as shown for example in U.S. Pat. No. 3,286,508, or by detecting the passage of light through the filter, as shown for example in U.S. Pat. No. 3,484,772.
It is also known to use various single purpose sensors to monitor the dryness of the clothes load in a dryer. For example, it is known to detect dryness by detecting the conductivity of the clothes using a pair of electrode sensors, as shown for example in U.S. Pat. No. 3,593,571, or by discharging a capacitor into the clothes, as shown for example in U.S. Pat. No. 4,422,247. Still another technique is to measure exhaust air temperature, as taught by U.S. Pat. No. 3,203,679. This dryness information is either used directly or indirectly to control the length of a drying cycle or the energization of the heater. In U.S. Pat. No. 4,385,452, for example, a microcomputer seeks a preset number of consecutive "dry" readings from the sensor before it will act to regulate the drying cycle.
Still other sensors and controls are known in the art for controlling dryers. In U.S. Pat. No. 3,507,052, a dryer control is described which senses a load tumbling pattern and uses this information to set the speed of the motor so as to provide an optimum tumbling pattern. In U.S. Pat. No. 3,874,089, a dryer control is described which senses the energization of the heater and uses this information to control the motor.
Each of these prior art designs uses a single type of sensor to monitor a single characteristic and to control a single function of the dryer. None of these references provide a control circuit that is adapted for monitoring the function of the motor and the heater using a single circuit to monitor several diverse characteristics of the operation of the dryer and to provide complete control of the dryer operation.
3. Description of Related Applications
In copending patent application Ser. No. 392,368 filed Aug. 11, 1989 entitled ELECTRONIC CONTROL FOR AN AUTOMATIC WASHING MACHINE WITH A REVERSING PSC MOTOR (Bashark II), a control system for an apparatus having a permanent split capacitance motor was disclosed using phase angle information obtained by a ferrite core sensor monitoring at least one winding of the motor when the motor is deactivated so as to determine loading information about the apparatus. In the preferred embodiment, the apparatus disclosed is an automatic washer having a basket which is reciprocally driven during an agitation cycle by alternatively operating the motor in a clockwise direction and in a counterclockwise direction. The basket is also continuously driven in a single direction by the motor during a spin cycle.
In particular, information about the clothes load is obtained by monitoring the zero crossings of alternating current in a winding of the motor. In order to sense zero crossings of alternating current in a winding of the PSC motor, a ferrite core transformer sensor is employed having a primary winding that includes at least one turn of a motor winding and a secondary winding at which the current zero crossing signal is generated. In the preferred embodiment, two ferrite core transformer sensors are used, one monitoring a first motor winding and one monitoring a second motor winding.
The control system senses zero crossings whether the motor is currently on or off. When the motor is off, the residual current, that is, the current generated by the continuing motion of the motor, is substantially unaffected by the line voltage. It is during the hesitation period, after the motor has driven the basket and has been cycled off, that braking action occurs. The duration of residual alternating current during the hesitation period is inversely proportional to the breaking force on the motor and the breaking force is, in turn, an indication of the size of the clothes load in the basket. Thus, the control can provide a representation of the size of the clothes load, which can be used to regulate various operations of the washer, such as the amount of water needed, cycle time, whether or not to agitate during fill.
The control system in Bashark II also improved on the control of Bashark I by providing improved control circuitry and logic and by teaching the control of several additional operations of the automatic washer.
In copending patent application Ser. No. 392,473 filed Aug. 11, 1989 entitled ELECTRONIC CONTROL FOR AN AUTOMATIC WASHING MACHINE WITH A REVERSING PSC MOTOR (Bashark III), the same control system as disclosed in Bashark II is used to monitor a permanent split capacitance motor while it is actually operating under power. In particular, the motor is monitored using a ferrite core sensor while it is driving the basket of an automatic washer to determine when the motor has reached operating speed or to detect the amount of dither in its operation. This information provides a representation of clothes load during a spin cycle, which is then used to regulate the duration of spin and to detect off-balance conditions.
In particular, the control uses the phase angle representation to detect a characteristic increase in the motor phase angle to determine the motor start time, that is, the amount of time that it has taken for the motor to reach operating speed. An auto-referencing technique is employed by which the motor start time is auto-referenced to the minimum sum of two consecutive phase angle representations. From the motor start time, the electronic control determines the size of the load in the basket and then determines the spin time from the size of the load.
The electronic control further employs an auto-referencing technique to detect an unbalanced load condition in the basket. The control compares the motor phase angle samples taken from either positive or negative line half cycles, which provides a representation of the amount of dither experienced by the motor.
In a patent application, intended to be filed but not filed as of the time of allowance of the present application, entitled ELECTRONIC CONTROL FOR AN APPLIANCE (Bashark IV), the same control system as disclosed in Bashark II and Bashark III is described and claims are presented directed to the novel features of the control circuit itself. Since the preferred embodiment of the inventions claimed in Bashark II through IV were identical, the disclosures of these applications are nearly identical.
In copending patent application Ser. No. 397,755 filed Aug. 23, 1989 entitled ELECTRONIC CONTROL FOR A DOMESTIC REFUSE COMPACTOR (Bashark V), a control circuit very similar to the control circuit disclosed in Bashark II through IV is disclosed for monitoring an inductance motor to detect the onset of stall of the motor. The control uses the ferrite core sensor to monitor the operation of an apparatus to detect a characteristic change in the phase angle measurements indicative of the onset of stall and uses this information to regulate the operation of the apparatus. The control responds to the detection of the onset of stall by temporarily increasing torque, by shutting down the motor, or by providing user information indicative of the timing of the occurrence.
As in Bashark II and in Bashark III, the control logic used in Bashark IV is auto-referenced. The onset of stall is detected by detecting when the phase angle reaches a level substantially equal to a previously measured locked motor phase angle or, alternatively, when the phase angle measurements exceed the maximum phase angle measurements set earlier in the same operating cycle.
In particular, Bashark V provides a refuse compactor with an inductance motor reciprocably driving a ram into a compartment containing refuse to be compacted. The electronic control treats the detection of the onset of stall as the detection of the onset of compaction. The control provides a choice of compaction cycles that provide different full bag weights, depending on the indicator of onset chosen and depending on the response chosen. For example, a higher compaction force than is otherwise available from the motor is obtained by temporarily energizing the start winding of the motor when the onset of stall is detected, thereby providing increased torque at the time when the most work is being done by the compactor. A comparatively lower torque level is obtained by stopping the motor when the onset of stall is detected by one of the two methods disclosed.
The fullness of the refuse receptacle is determined by measuring the time that the motor has been operating prior to the detection of the onset of stall. A full bag or empty bag condition can also be detected and signalled to the operator when the time period is extremely short or long.
In present patent application (Bashark VI), a control circuit very similar to the control circuit disclosed in Bashark II through V is disclosed for monitoring an inductance motor to detect a non-cyclical change in the load experienced by a motor. The control uses the ferrite core sensor to monitor the operation of an apparatus to detect a characteristic change in the phase angle measurements indicative of non-cyclical change and compensates for the effect of cyclical changes. The control uses this information to regulate the operation of the apparatus. The control responds to the detection of the non-cyclical change by shutting down the motor, by varying the operation of other systems, or by providing user information indicative of the timing of the occurrence.
As in the earlier applications, the control logic used in the present application is auto-referenced. The non-cyclical change in loading conditions is detected by a voting process detecting whether the slope of the last six, seven, eight or nine clothes tumbles numbers is increasing or decreasing, respectively and, immediately after each computation, voting for or against the clothes load being dry in accordance with whether the computed slope is negative or positive, respectively.
In particular, the present application provides a dryer with an inductance motor rotatably driving a drum containing wet clothes to be dried. The electronic control treats the detection of the change in load conditions as the detection of drying, since dry clothes tumble differently than wet clothes. The dryness of the clothes is determined by measuring the phase angle of a winding of the motor and the clothes are considered to be dry when the variation in phase angle due to clothes tumbling is no longer decreasing.
In copending patent application Ser. No. 07/460,269 entitled HEATER DIAGNOSTICS AND ELECTRONIC CONTROL FOR A CLOTHES DRYER filed concurrently with the present application on Jan. 2, 1990 (U.S. Pat. No. 5,101,575) uses a circuit and logic similar to that disclosed in Bashark II through VI to monitor the operation of an apparatus having a motor and heater and to control the operation of the apparatus in response to heater current information. In particular, the control is used to operate a clothes dryer and is therefore further modified from the disclosures of Bashark II through V to provide several novel features uniquely advantageous for the operation of a clothes dryer.
Since the preferred embodiment of the inventions claimed in Bashark VII and in the present application are identical, the disclosures of these two applications are nearly identical.
4. Objects of the Present Invention
It is a primary object of the present invention to provide a diagnostic system for a dryer to detect when the clothes are dried to a predetermined dryness by monitoring characteristics of the motor rotatably driving the dryer drum.
More particularly, it is an object of the present invention to provide a method and an apparatus for monitoring the current in a winding of the motor to determine the tumbling characteristics of the clothes in the dryer such as to detect changes in the manner in which the clothes are tumbling that would indicate that the clothes have reached a predetermined level of dryness.
It is also an object of the present invention to provide a control to regulate the duration of operation of the dryer drum and/or the duration of operation of the dryer heater in response to the detection of the clothes attaining a preselected level of dryness.
It is another object of the present invention to provide a method and an apparatus for monitoring any motor under a cyclically varying load for non-cyclical changes in motor winding which are indicative of non-cyclical changes in the load.
It is yet another object of the present invention to provide a control for a motor driven apparatus, and especially for a dryer, which compensates for the effect of cyclical changes on the loading of the motor and which controls the operation of the motor driven apparatus in response to the detection of a non-cyclical change in the loading on the motor.
It is still another object of the present invention to provide a control for a motor driven apparatus, and especially for a dryer, which compensates for the effect of cyclical changes on the current in a winding of the motor and which controls the operation of the motor driven apparatus in response to the detection of a non-cyclical change in the current in a winding of the motor.
It is still yet another object of the present invention to provide a method and an apparatus for monitoring the functioning of an appliance having a motor and a heater by monitoring the current through the heater.
It is a further object of the present invention to provide a control for a motor and the heater responsive to the detection of current in the heater.
It is a still further object of the present invention to provide a method and an apparatus for monitoring the functioning of an appliance having a motor and a heater by monitoring the current through the heater and the current through a winding of the motor using a single sense winding and a single control.
It is another object of the present invention to provide a control for a motor and the heater responsive to the detection of current in the heater and the phase angle of the motor.
It is still another object of the present invention to provide a dryer control providing a clothes cooldown period with controlled moisture regain as per the user dryness selection.
It is yet another object of the present invention to provide an exhaust air temperature sensor that uses the same control circuitry as the dryness sensor and requires only the addition of a thermistor in the exhaust line.
It is a further object of the present invention to provide a dryer having a sensor capable of detecting numerous diagnostic conditions at the start of each cycle, or throughout each cycle, such as, 208 or 240 VAC service voltage identification, motor start, drum acceleration, empty drum, motor open/short circuit, open door, broken belt and, restricted air flow.
These and the many other objects, features, and advantages of the present invention will become apparent to those skilled in the art when the present application is read in conjunction with the drawings appended hereto.